Among the characteristics of photoresists to be used in fine processing for the production of semiconductors and electronic devices such as liquid crystal devices, fluorescent display tubes, thermal heads and image sensors, adhesiveness to the surface of a base board to be etched is particularly important. Common positive-type photoresists frequently suffer from peeling or undercut caused by wet-etching with a strong acid or a weak base. It has been attempted, therefore, to treat the surface of a base board to be etched with, for example, hexamethyldisilazane so as to improve the adhesiveness. However such a treatment does not provide a satisfactory effect. It has been further attempted to heat a base board before or after the application of a positive-type resist or after development, though the effect thus achieved is limited.
JP-B-50-9177, JP-B-54-5292 and JP-A-53-702 each disclose a method for the improvement of the adhesiveness to the copper surface of a print base board (the terms "JP-B" and "JP-A" as used herein respectively mean an "examined Japanese patent publication" and an "unexamined published Japanese patent application"). However each of the disclosed photosensitive materials is the negative-type photoresist which is exclusively applicable to a copper base board.
In the field of fine processing, positive-type microphotoresists having high resolving power have been mainly employed. However no effective additive such as an adhesion aid for positive-type photoresists has yet been known. In the field of processing electronic devices such as displays or thermal heads, wherein base boards made of various materials are employed, no effective additive has been found thus far, since the adhesiveness of the photoresist would vary depending up on the base boards used.